Fermentation process

ABSTRACT

The process of handling fermenting medium such that the carbon dioxide released during fermentation is applied to the problem of creating an agitation regime for desirable product quality and heat dissipation, and apparatus having depth and bottom shapes that determine the agitation pattern and assist in heat dissipation.

United States Patent [191 Delente et al.

FERMENTATION PROCESS Filed: Feb. 22, 1971 Appl. No.: 117,821

Related U.S. Application Data Continuation of Ser. No. 695,274, Jan. 2, 1968, abandoned.

U.S. Cl. ..99/3l, 99/276,195/144 Int. Cl ..Cl2c 11/04, Cl2b l/OO Field of Search ..99/3l, 276, 277;195/139, 143,

References Cited UNITED STATES PATENTS 9/1965 Pollock ..'...T...99'/-3i Jan. 30, 1973 3,415,654 12/1968 Zinn ..99/31 3,374,726 3/1968 Takayanagi ..99/275 FOREIGN PATENTS OR APPLICATIONS 274,225 7/1927 Great Britain ..99/31 Primary Examiner-A. Louis Monacell Assistant Examiner-David M. Naff Att0rneyGrave1y, Lieder and Woodruff [57] ABSTRACT The process of handling fermenting medium such that the carbon dioxide released during fermentation is applied to the problem of creating an agitation regime for desirable product quality and heat dissipation, and apparatus having depth and bottom shapes that determine the agitation pattern and assist in heat dissipation.

3 Claims, 10 Drawing Figures PATENTEDJAHSO I975 3, 713.839

- SHEET 1 BF 4 5 M M Fa/mag? 1 FERMENTATION PROCESS capacity and with a depth for the medium of not much greater than 9 feet. The fermentation tank size has also been governed by the capacity of available transportation and load limitations imposed thereon. It is also a characteristic of conventional fermenters that size should not be excessive or there would be trouble in dissipating the heat. In addition, prior ferrnenters required manual yeast harvesting by workers actually getting into the same and this raised the chances of contamination. Also, their shape was not suited to be spray cleaned effectively. In spite of technical skills available today, the handling of large batch fermenting medium has not changed to any significant extentover what it has been in the past.

In the present invention the object is to provide a novel batch fermentation process.

It is also an object of this invention to provide a novel process for alcoholic fermentation, and especially beer fermentation.

As another object of this invention there is the provision of a significant advance in the fermentation process where gas is released in substantial amounts, as

either the main or the side reaction of the overall fermentation action, and is applied to the work of agitating the fermenting medium.

A further object of this invention is to provide apparatus that will promote and enhance the effectiveness of a fermentation process for the production of alcoholic media or beer.

Yet another object of this invention is to provide ap paratus that will develop a hydro-dynamic circulation regime without reliance on externally powered agitation means.

Another object of this invention is to provide apparatus having a particular configuration for the purpose of establishing and promoting a desirable hydrodynamic system of agitating a fermenting medium so as to enhance desired qualities in the end fermentation product and to effect the foregoing general and specific features in an economical manner without requiring externally operated agitating equipment.

It is yet another object of the present invention to provide a large capacity fermenter having a significant depth and to shape the bottom surface of the fermenter so as to take advantage of the power generated by the carbon dioxide release, the carbon dioxide creating internal agitation in the fermenting medium in a predetermined desired hydro-dynamic regime that will coincide with and enhance the natural convection currents and substantially reduce the difficulties heretofore encountered in effecting heat transfer out of a large fermenter.

A further object of the invention is to provide a fermentation process and apparatus for promoting such a process that will utilize the fermentation energy to create proper agitation within the fermenting medium.

It is yet another object of the present invention to provide a large capacity fermenter having a significant depth and to shape the bottom surface'of the fermenter so as to take advantage of the power generated by the carbon dioxide release, the carbon dioxide creating internal agitation in the fermenting medium in a predetermined desired hydro-dynamic regime that will substantially reduce the difficulties heretofore encountered in effecting heat transfer out of a large fermenter. A further object of the invention is to provide a fermentation process and apparatus for promoting such a process that will utilize the fermentation energy to create proper agitation within the fermenting medium.

More specifically the present invention is directed toward the provision of a power difference at different zones in a fermenter, and this is accomplished by applying certain desired configurations to the fermenter bottom such that the power difference is localized and controlled to produce the desired fluid regime which has its orgin at predetermined parts or areas of the fermenter bottom.

Other objects and advantages of the presentinvention will be set forth in the following specification which will describe-a preferred process and apparatus adapted for beer fermentation, but it is not to be limited to such fermentation. The specification will be presented in more detail in connection with the accompanying drawings wherein:

FIGS. 1 and 1A are graphs to illustrate certain characteristics of beer fermentation, and in FIG. 1 the graph specifically relates fermentation phases with the amount of carbon dioxide gas released, and in FIG.' 1A the graph relates the rate of CO production with time:

FIG. 2 is another graph which represents conditions taking place within the fermenter according to the objects of the present invention, the graph setting forth in particular the relationship of carbon dioxide bubble velocity to its level in the fermenter;

FIG. 3 and FIG. 3A are respectively a schematic sectional elevational view and a transverse section at line 3A3A in FIG. 3 of a deep fermenter having a bottom configuration that conforms to the criteria for the present invention;

FIG. 4 is a view similar to FIG. 3 but showing an inversion of the bottom configuration for a deep fermenter; 1 I

FIG. 5 and FIG. 5A are respectively a schematic sectional elevational view and a transverse section at line 5A--5A in FIG. 5 of a fermenter having a deep zone;

and

FIG. 6 and FIG. 6A are, respectively, a schematic sectional elevational view and a transverse view at line 6A-6A in FIG. 6 showing a fermenter having a sloped bottom.

It has been observed in beer fermentation that the fermentation pattern follows substantially that shown along line A in FIG. 1 where the fermentation passes through a lag phase, then an active fermentation phase, followed by end fermentation. The graph indicates that during the time interval (as measured along the horizontal) in which the fermentation takes place, carbon dioxide is generated in an amount that begins in the lag=phase and continuesquite strongly during the active fermentation phase before it decreases during the end fermentation phase. It has also been observed during the active fermentation phase that the rate of carbon dioxide and alcohol formation is practically constant as is depicted by the line B, as shown in FIG. 1A, even though the temperatures of fermentation may be different. It is, of course, understood that the slope of the curve A and the plateau of curve B change according to the temperature. The wort composition and the type of yeast used also has an effect on the pattern of the graph lines A and B.

It has been discovered that the carbon dioxide bubbles form only on the bottom surface of the fermenter and that no bubbles are formed in the body of the liquid although fermentation takes place throughout the liquid. The composition of the fermenting medium is substantially uniform throughout a deep fermenter and there is no concentration or stratification although there are apparent hydro-static variations. Such discoveries have been made on the basis of observations so that it is now known that bottom surface bubble formation is the rule and that all bubbles are of about the same size when they reach the surface. It is also known that the distribution of yeast, sugars, alcohol, are homogeneous in a deep fermenter. From such observance it is concluded that the rate of diffusion of carbon dioxide from the liquid into the ascending gas bubbles is-rapid and with little resistance. It takes a greater amount of energy to overcome the liquid cohesion and form a new phase than for the gas to diffuse from the liquid into an already formed bubble. As will appear in more detail presently, the process is specifically to provide power differences at different zones of a fermenter, and this is done by the physical configurations of the fermenter so that the power difference is localized to produce a controlled fluid regime.

During fermentation, and the following description will be substantially limited to beer fermentation without strict limitation thereto, numerous bubbles form at the bottom and'rise through the liquid to sweep the excess carbon dioxide from the liquid at so rapid a rate that no additional bubbles are formed. In FIG. 2 it can be seen that the velocity of the bubbles follows about the curve C which means that initially there is a rapid rise that falls off as the bubbles get further away from the bottom surface. The effect of the formation of the bubbles at the bottom of the fermenter can be mathematically evaluated as follows:

Since the concentrations of yeast and substrate are homogenous the rate of CO production is the same at any point of the fermenter and all the bubbles will pick up equivalent amounts of gas H420, for every unit of distance Ah traveled1 w- Ah where K is a constant in given fermenting conditions.

If the bottom of the fermenter is an homogenous surface, all' the bubbles will start with the same size and. will contain equal amounts of gas. Therefore the mass of gas inside of a bubble varies proportionally to the levelhin the fermenter: i i v If P is atmospheric'pressure, p the specific mass of beer, 8 the acceleration due to gravity, v the volume of a bubble and II the height of the liquid in the fermenter, and if we consider CO, as a perfect gas, we

have

Let us call H the height of beer equivalent to atmospheric pressure:

H PA/pg 4. and we obtain r "arm The initial volume V of a bubble as it leaves the bottom of the fermenter is such that V pg 'rrdo 6. where 0' is the surface tension and d the theoretical orifice diameter of the nucleation site. In a smooth surfaced fermenter d is small enough so that expression 5 was always experimentally verified.

The bubbles move upwards due to the buoyancy force F,,. Since the mass of the bubble is very small, it should be subjected to a very high acceleration but it is slowed down by the drag force F,,. In fact, the speed of the bubble is very small, compared to the value it would reach without the drag force. Practically all the energy available to the bubble by the buoyancy force is transmitted to the liquid by the drag force:

F F G 7, e gives the kinetic energy to the bubble, and makes a work F, pa 9. The work W, accomplished by one bubble is by definition l H K Hxpghdh from 10 and 11 Integration by change of variables and by partsgives:

W1; K gH (HA+H (in The higher the fermenter, the more work a bubble will yield. Let us express the available power P due to the bubbles in a cylindrical vertical fermenter of a given volume B, where we are designing different crosssections S and heights H.

B SH 14. Since the fermentation conditions are the same and the bottom surface is homogenous, the number of bubbles produced per unit of time, N is proportional to the cross-section:

At steady state the power P is by definition P=NW,= K SW K BWJH l6. tfliii .4--

HA+ H HA H PK K pgB HA H 111 --*HA 1] 1 7- Let us multiply expression by expression 2:

NXMCOZ =K K SH 18, At the top of the fermenter h H and NMCOZ is the total amount of gas produced per unit of time. If QEF, is the rate of gas production per unit of fermenting volume, we have:

Another method of computation, where the effect of hydrostatic head was included after integration, yielded the following expression of power.

HA BQCOQPQ P: 2 H1+ 2 22.

For heights up to 60 feet the two formulas give near'ly identical'values of power. However,.formula 2l is a better theoretical expression of the phenomenon.

Many other methods of calculation are available to compute the power, for example a graphical method where the drag coefficient C and the bubble velocity u are the base of calculation:

u 43d/C 23.

All methods give sensibly the same values to the bubble. power. For example an upright cylindrical fermenter containing 5,600 bbls of fermenting beer, 30 feet high, would yield a power P 2.25 HP according to expression 22 P= 235 HP according to expression 21 P 2.18 HP according to graphical method All of the aforementioned observations and related calculations indicate that a dynamic state is established by the CO generation, and that the CO bubbles irnpart an amount of power to the fermenting medium. By taking advantage of this power input by the bubbles, a positive circulation current can be produced, which will: (l) improve the heat transfer efficiency of the attemperating jackets, (2) accelerate the fermentation process by causing a more intimate mixing of yeast cells and nutrients, (3) speed up the liberation of C0 (4) produce a product with more uniform qualities.

It is also a recognized observation that the circulation regime is by convection motion arising from differences in density in the fermenting medium and also due to the heat of fermentation. The power derived from the'bubble motion enhances the natural convection currents.

Since the power input by the bubbles to the fermenting medium increases with the height of the fermenter, a fermenter should be relatively deep for a given volume, within certain limits, in order for the bubbles to produce a maximum amount of power for circulations. Tobe more specific, a fermenter should not be too narrow, for this will restrict circulation and the desired regime will not be accomplished. Furthermore, the shape and proportions of the fermenter, specifically the ratio of height to diameter and the shape of the bottom, should be such that these factors will facilitate achievement of the desired regime.

Therefore the invention is related to a fermentation process where the reaction or product stratification is eliminated, and the heat of fermentation is uniformly removed from the fermenting medium without the application of externally induced agitation, but with the establishment of the proper fluid regime by the use of internally generated energy with the apparatus or fermenters as illustrated in the following examples:

Attention will now be directed to FIG. 3 where a typical fermenter tank is shown having at least 20 feet of vertical wall and the vertical wall is circular with a diameter of approximately 20 ft. The fermenter tank shown at 10 is provided with a cone bottom 11 in which the slant angle of the cone surface or the pitch of the bottom is approximately 30, but may vary from about 7 to about In a fermenter of this physical configuration a fluid circulation regime takes place upwardly at the center of the cone and downwardly adjacent the walls: since the average liquid height at and near the center of the cone is greater than the average height at and near the wall, the power input by the bubbles rising in the zone represented by a theoretical tubular partition 12 will be greater than the power input by the bubbles moving upwardly in the annular space 13 outside of the theoretical cylinder 12. It is assumed (FIG. 3A) that the cross sections inside and outside the theoretical partitions 12 are equal, and that R is the radius of the fermenter tank 10, Ri is the radius of thepartition 12, and S is the cross section of the fermenter. Under this condition, we then have the equations:

8/2 1r Rl2 1rRi" and Ri= (R @2 )/2 It is also necessary to consider the following AH=vertical distance between cone base and cone side.

AH =AH at the apex Rtga AH,,=AH at the partition AH average AH inside of partition AH,,=average A H outside of partition AP difference of power due to AH, which will establish the fluid regime AP P inside of partition P outside of partition HA Qco Pg Riga H +H 2 2 2 n U iiiiiiiiii b H it"? LIL 3w 2 2 2 will establish the discharge fluid regime can be calcu- I lated easily if it is assumed that the volumeabove the deep zone is equal to half the total volume. We then have the circulation current if all of the nucleation can be concentrated in a chosen area ofthe fermenter bottom surface.

It has been determined by laboratory observation that nucleation of the carbon dioxide bubbles occurs in the chosen or predetermined area of the bottom of the fermenter, and it has also been observed that as the fluid regime gets established, the motion thereof concentratesthe yeast in the bottom area of the cone or in the deepest part of the fermenter tank which would be the circumferential area 20 in the fermenter shown in FIG. 4 or the lowest surface in the deep zone fermenter shown in FIG. 5.

In the fermenter tank 17 of FIGS. 6 and 6A the concentration of yeast will occur in the deep zone 18. It has also been observed that the" liquid moves fast enough so that very little nucleation takes place at the highest points or surfaces of the fermenterbottom.

In the fermenter tank 15 shown in FIG. 5 it may be sized with a vertical side wall varying from about 20 to about feet, the diameter of such a tank may vary from about 20 feet to about 60 feet, the diameter of the deep zone 16 may vary from about 14 feet to 42 feet, and the overall vertical height including the enlarged tank section and the deep zone 16 may vary from about 30 feet to as much as 70 feet.

In the various fermenters shown in the accompanying drawings, and for shapes other than those shown, the bottom surface should have sufficient slope toward the outlet pipe so that the yeast can be removed by means of an automatic in-place spraying system. A suitable spray system is seen in FIGS. 3, 4 5 and 6 where a spray head 19 within the fermenter tank is supplied by pipe 20 with the spray fluid. The pipe 20 is disposed substantially centrally while a vent 21 is located adjacently to discharge carbon dioxide. This will'avoid the necessity of manually cleaning the fermenter tanks as is required in conventionalfermenters. It has been found that the bottom slope should have at least the minimum pitch of about 7.

In the foregoing drawing of the fermenter there is provided a cooling system of more or less conventional character in which the cooling jacket 23 is carried as a belt surrounding the outer wall of the fermenter where the circulation regime is such that the down flow moves adjacent the fermenter wall cooled by the cooling jacket. The jacket 23 is suitably connected to any convenientrefrigeration equipment illustrated at 24. Thus the heat of the fermentation may be removed from the fermenter medium without the application of externally powered paddles or equivalent agitating device. In place of the latter the fluid regime itself when established will maintain a circulation that will constantly carry. the heat generated during the fermenting A H in the foregoing formula is the height of .the deep zone 16, and it will appear that the deeper this deep zone is made the easier it will be to establish the fluid regime. I

It will also appear now that all of the available power from the gas discharge bubbles may be used to enhance The foregoing description has set forth the principles of this invention, and has also described certain fermenter configurations by which the invention may be practiced. In view of the above it is the intent hereof to include relevant fundamental fermenter configurations and steps in the practice of the invention within the scope of the appended claims.

What is claimed is:

l. A batch fermentation process for making beer and related beverages which consists in the steps of:

1. providing a fermenter which opens upwardly in a diameter of at least 20 feet, and has a depth of at least 20 feet and a closed conical bottom surface sloped from about 7 to 70 to its deepest zone filling the fermenter to a height of at least 20 feet with a volume of wort and fermentable yeast to carry out fermentation 3. allowing the mixture of wort and yeast to ferment in the fermenter;

. allowing yeast cells to collect at the fermenter bottom to focus carbon dioxide bubbles nucleating at the bottom of the fermenter from said yeast in a rising flow within the batch;

5. agitating during said fermentation solely by the power derived from said rising flow of carbon dioxide bubbles from said yeast to induce and maintain a circulation regime of upward and downward currents within the batch for mixing and to carry the heat of fermentation to zones where the heat can be extracted;

. extracting the heat of fermentation from the batch in the zones thereof outside the focused rising flow; and

7. utilizing as the sole means of agitation the agitation created by said bubble power and said heat extraction to maintain the circulation regime during the entire fermentation process.

2. A batch fermentation process for making beer and related beverages which comprises the steps of:

l. containing a batch of wort and yeast having a height of at least 20 feet in a fermenter having a depth of at least 20 feet, a diameter of also at least 20 feet, and a bottom surface sloped at from about 7 to to its deepest zone;

. allowing the batch to ferment in the fermenter to carry out fermentation;

3. allowing yeast to collect in the deepest zone such that carbon dioxide bubbles nucleating at the bottom of the fermenter from said yeast are focused from said deepest zone upwardly in a rising flow through the batch;

. agitating during said fermentation solely by the power of said rising carbon dioxide bubbles to provide a circulation regime of upward and downward currents for mixing the fermenting batch and to carry the heat of fermentation to zones not in the rising flow;

5. extracting the heat of fennentation of the batch from the zones not in the rising flow; and

6..utilizing as the sole means of agitation the agitation created by said bubble power and said heat extraction to maintain the circulation regime during the entire period said wort and yeast are present in said fermenter. 3. A fermentation process according to claim 2 wherein the upward current of the circulation regime is in the center of the fermenter and directly above the deepest zone thereof, and the downward current is adjacent the side of the fermenter. 

1. A batch fermentation process for making beer and related beverages which consists in the steps of:
 1. providing a fermenter which opens upwardly in a diameter of at least 20 feet, and has a depth of at least 20 feet and a closed conical bottom surface sloped from about 7* to 70* to its deepest zone
 1. containing a batch of wort and yeast having a height of at least 20 feet in a fermenter having a depth of at least 20 feet, a diameter of also at least 20 feet, and a bottom surface sloped at from about 7* to 70* to its deepest zone;
 2. A batch fermentation process for making beer and related beverages which comprises the steps of:
 2. filling the fermenter to a height of at least 20 feet with a volume of wort and fermentable yeast to carry out fermentation
 2. allowing the batch to ferment in the fermenter to carry out fermentation;
 4. agitating during said fermentation solely by the power of said rising carbon dioxide bubbles to provide a circulation regime of upward and downward currents for mixing the fermenting batch and to carry the heat of fermentation to zones not in the rising flow;
 4. allowing yeast cells to collect at the fermenter bottom to focus carbon dioxide bubbles nucleating at the bottom of the fermenter from said yeast in a rising flow within the batch;
 5. agitating during said fermentation solely by the power derived from said rising flow of carbon dioxide bubbles from said yeast to induce and maintain a circulation regime of upward and downward currents within the batch for mixing and to carry the heat of fermentation to zones where the heat can be extracted;
 5. extracting the heat of fermentation of the batch from the zones not in the rising flow; and
 6. extracting the heat of fermentation from the batch in the zones thereof outside the focused rising flow; and
 6. utilizing as the sole means of agitation the agitation created by said bubble power and said heat extraction to maintain the circulation regime during the entire period said wort and yeast are present in said fermenter.
 7. utilizing as the sole means of agitation the agitation created by said bubble power and said heat extraction to maintain the circulation regime during the entire fermentation process. 